Process for inhibiting foaming in steam boilers



Patented May 10, 1949 PROCESS FOR INHIBITING FOAMING IN STEAM BOILERSPaul G. Bird and Arthur L. Jacoby, Western Springs, 111., assignors toNational Aluminate Corporation, Chicago, 111., a corporation of DelawareNo Drawing. Application September 19, 1942, Serial No. 459,012

4 Claims.

The present invention relates to antif-oaming compositions which areused in steam boilers and similar steam generators, evaporators, etc, toovercome the tendency of the water therein to foam and hence to bringabout the priming of the steam generator or the like.

One of the objects of the present invention relates to a liquid suitablefor the generation of steam in steam generators and comprising Watercontaining therein a very small quantity of an N,N'-disubstituteddiamide of an organic dibasic acid, whereby, when such water is heatedto the boiling point in a steam boiler or other generator, being therebyevaporated, the concentration of solids therein will not bring aboutexcessive foaming and the resulting priming, these compounds beingsubstantially nonvolatile with the steam and stable, so that they willbe retained by the water and neither they nor their decompositionproducts will appear in the steam and the resulting condensationthereof.

It is well known in the operation of steam boilers, such as in electricpower plants, railroad locomotives and the like, or in evaporators, thatthe water therein, even though initially it shows very little tendencyto foam, will, when the amount of total solids therein approaches arelatively high concentration, develop a very decided tendency to foam.When this occurs, considerable quantities of water are physicallycarried out of the boilers or evaporat-ors with the steam, thusappearing in the steam lines and in the eventual condensate. Suchpriming has ma di d tages because it tends to contaminate the steamlines, to plug or corrode the valves, and under serious conditions mayeven impair the cylinders and piston rods of the steam engines, or theimpeller blades of turbines in which the steam is used for thegeneration of power. Attempts have been made in the past to control thisfoaming, either by excessive blowdown of the boilers or by the injectionthereinto of such materials as castor oil, tallow, and the like. Whilethese fatty materials have some small degree of efficiency, they are, onthe other hand, quite deficient in that they introduce new dilficultieswhich, in some instances, are worse than the conditions they areintended to cure. In the first place, these fatty acids or glyceridesare unstable under the conditions existing in the boilers, particularlyas the pressure and temperature increase, the high temperatures leadingto rapid decomposition of the glycerides, which, if anything, will tendto increase the foaming and priming diificulties. Furthermore, in manyinstances certain of the decomposition products thus produced, orsometimes even the materials themselves, have a definite volatility withsteam and will, therefore, steam-distil out of the boilers, thusappearing in the steam and in the condensate. This, of course, is alsovery undesirable. Furthermore, such types of antifoaming agents usuallyhave to be employed in relatively large quantities, adding not only tothe expense but also to the inconvenience of operating the steamgenerators; and those which have a tendency to decompose do so quiterapidly, and hence their efiectiveness is of short duration, whichtherefore necessitates the continual charging into the boilers or othersteam generators of relatively large amounts of these older antifoamingagents. Moreover, such antifoaming agents are diflicult to use becausethe amounts in which they are efiicacious are very critical, and anyoverdosage usually aggravates the difiiculty instead of curing it.

Applicants have now discovered, however, that there is a series ofcompounds which may be broadly designated as N,N'- disubstituteddiamides of organic dibasic acids, wherein the substituent groups may bederived from aliphatic primary or secondary amines, or amine-containingbodies; in which the dibasie acids may be either aliphatic, aromatic, oraryl-aliphatic, and may contain hetero atoms between the carboxylgroups; and the molecular weight and configuration conform to certaingeneral specifications; all as more fully described hereinafter, whichare highly eflicacious to suppress foaming.

The materials employed in the practice of the present invention may berepresented by the general formula:

H H R-b'I-O c-X-c od s wherein R and R are aliphatic radicals derivedfrom aliphatic primary or secondary amines or from more complexaliphatic and arylaliphatic amine-containing bodies as, for example,alpha alkylbenzylamines, C-alkylanilines, m-onoacylalkylenediamines,alkylalkylenediamines, partially acylated polyalkylenepolyamines,monoacylpiperazines, monoacylhydrazines, and the like; and X is analkylene or arylene radical which may contain hetero atoms, so that thegroup --OCXCO represents the diacyl radical of a dibasic carboxylicacid. The radical -OCXCO- may thus be the residue of a dibasic acid suchas adipic, pimelic, suberic, sebacic, azelaic, lora-ssilic, japanic,phthalic, terephtha-lic, and naphthalic. It will be obvious that whenthe amide linkages are formed product of about 2 mols of hexadecylamineand REFERENCES CITED about 1 mol of azaleic acid, said quantity being Tsuificient to substantially inhibit foaming and z fig gg i fg are ofrecord m the priming.

4. The method of generating steam which com- 5 UNITED STATES PATENTSprises boiling, under superatmospheric pressure Number Name Dateconditions, water containing an amount of total 1 892 857 speumeyer Jan3 1933 dissolved solids tending to produce foaming and 2304475 P001 1942priming, and a quantity of the condensation 2:328:551 g ggfi1:1;111';sepil 1943 product of about 2 mols of hexadecylamine and 10 about 1 molof suberic acid, said quantity being sutficient to substantially inhibitfoaming and priming.

PAUL G. BIRD.

ARTHUR L. JACOBY. 15

